Department of Aerospace (2013 - Present)
Aerospace Engineering - Flight Dynamics and Control
Aerospace Engineering, Khaje Nasir al-Din Tusi University of Technology, Tehran, Iran
Aerospace Engineering - Flight Mechanics
Aerospace Engineering, Khaje Nasir al-Din Tusi University of Technology, Tehran, Iran
Mechanical Engineering - Solid Design
Mechanical Engineering, Isfahan University of Technology, Isfahan, Iran
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Masoud Ebrahimi received his bachelors degree in mechanical engineering from Isfahan Technical University, Isfahan, Iran, in 2003 and his M.S. and Ph.D. degrees in aerospace engineering from K. N. Toosi University of Technology, Tehran, Iran, in 2006 and 2012. He is currently associate professor of the aerospace group at Tarbiat Modares Mechanical University. His research interests include: 1- Control, Guidance and Navigation of Flying Robots and Spacecrafts (Satellite Rendezvous) 2- Multidisciplinary Design Optimization of Aerospace Systems and Subsystems(Satellite and Launch Vehicles) 3- Optimization Algorithms 4- Celestial Navigation And Star Pattern Recognition Algorithms
The present study aims to present a guidance algorithm based on the relative motion prediction for orbital rendezvous, in which a coast phase is allowed between two powered phases. In both powered phases, the solution of the Hill-Clohessy-Wiltshire equations is used to find the required state variables at each time instant. To track the required trajectory and compensate for any orbital perturbations and uncertainties, a non-singular terminal sliding mode method is utilized as the steering law. Then, the finite time convergence of the state variables is mathematically proved. In addition, the starting time of the second powered phase is adapted to perturbations and uncertainties by another closed-loop algorithm during the coast phase. The p
In this study, a novel approach based on multi-objective genetic algorithm (MO-GA) is used for simultaneous tuning the unscented Kalman Filter (UKF) parameters and camera and inertial measurement unit camera calibration in a vision inertial navigation system (VINS). This system consists of visual odometry and inertial navigation system (INS) which integrates with a UKF. In order to obtain simultaneous tuning and calibration of the parameters and variables, the MO-GA minimises the root mean square error of the position and velocity of the vehicle on a selected trajectory of the benchmark data set. Then, the tuned parameters and calibrated variables are placed in the VINS and an adjusted VINS (AVINS) is obtained. For investigating the AVINS,
In this paper, a new methodology was proposed for finding optimal robust-reliable parameter values of a space-based earth observation (SEO) mission based on a predefined multi-purpose platform considering influential uncertainties and human judgment. A deterministic optimization was performed using an evolutionary algorithm on the basis of platform capability and mission-required performance, simulated by a dynamic simulation-based model. A set of non-dominated solutions with different behaviors emerged. Then, samples of these solutions were selected and an uncertainty analysis was carried out. After that, a multiple attribute decision-making (MADM) problem was formed with two groups of attributes related to constraints҆ violations and va
Uncertainty-based design optimization has been widely acknowledged as an advanced methodology to address competing objectives of aerospace vehicle design, such as reliability and robustness. Despite the usefulness of uncertainty-based design optimization, the computational burden associated with uncertainty propagation and analysis process still remains a major challenge of this field of study. The metamodeling is known as the most promising methodology for significantly reducing the computational cost of the uncertainty propagation process. On the other hand, the nonlinearity of the uncertainty-based design optimization problem's design space with multiple local optima reduces the accuracy and efficiency of the metamodels prediction. In th
Introduction: Chlamydia psittaci is an intracellular and zoonotic pathogen that is transmitted through contact with birds. This pathogen causes various clinical manifestations, including subclinical cases and fatal cases. On the other hand, the variety and low specificity of many of the symptoms make diagnosis difficult while early detection of the disease causes a significant reduction in mortality.Case Presentation: The patient was a 47-year-old man with a history of headache, fever, chills, dyspnea, and productive cough with a primary diagnosis of sinusitis, which was treated with co-amoxiclav. Due to the lack of recovery, the patient was hospitalized with the diagnosis of pneumonia and was treated with meropenem and levofloxacin. After
In the last two decades, the Visual–Inertial Odometry (VIO) has recently received much attention for efficient and accurate ego-motion estimation of unmanned vehicle systems. In particular, the VIO includes only an Inertial Measurement Unit (IMU) and a camera. In this paper, we present a novel calibration approach for accurate deployment of monocular VIO. For this purpose, the hybrid optimization algorithm is used for calibrating the camera intrinsic and camera–IMU extrinsic calibration, automatically and without knowing the mechanical configuration. It is a professional work to carefully calibrate the intrinsic and extrinsic parameters, and it is required to repeat this work when the mechanical configuration of the sensor suite changes
Although stock market bubbles play an important role in determining stock price and economic fluctuations, their explanation based on fundamental principles of the economy is a challenging task. The purpose of this paper is to identify the factors shaping the price bubbles of the Tehran Stock Exchange according to a Bayesian DSGE model in the real business cycles framework. Stock price bubbles in this model appear endogenously as a positive feedback mechanism that is supported by optimistic beliefs. Based on the obtained results, the sentiment shock was introduced as the most important source of bubbles fluctuations followed by fluctuations in the stock price. This shock reflects households’ beliefs about the relative size of bubbles and
The main purpose of this study is to determine the initial configuration of suborbital manned spacecraft in the conceptual design phase. During the suborbital flight path, stability of capsule is very important factor for the success of the mission. For this purpose, in this study using conventional manned spacecraft geometries which are generally blunt-cone shape, 5 configurations of space capsule are proposed. The configurations are numerically investigated during reentry phase at altitude of the 25 km from earth surface with Mach number 3.15 for different angles of attack. In order to determine longitudinal static stability characteristics of configurations during re-entry phase, the pitching moment coefficients of configurations are stu
Introduction: Chlamydia psittaci is an intracellular and zoonotic pathogen that is transmitted through contact with birds. This pathogen causes various clinical manifestations, including subclinical cases and fatal cases. On the other hand, the variety and low specificity of many of the symptoms make diagnosis difficult while early detection of the disease causes a significant reduction in mortality.Case Presentation: The patient was a 47-year-old man with a history of headache, fever, chills, dyspnea, and productive cough with a primary diagnosis of sinusitis, which was treated with co-amoxiclav. Due to the lack of recovery, the patient was hospitalized with the diagnosis of pneumonia and was treated with meropenem and levofloxacin. After
An efficient design is a key factor in final expenditure of a certain construction. Pressure vessels are structures that play an indispensable role in different industries such as petroleum, power plants etc. Pressure vessels are receptacles often used to keep gases or liquids at a pressure typically different from what atmospheric pressure is. End caps which close the end of vessels can be formed in different shapes. Thus, end cap design also has a significant role in the integrity of vessels to prevent fatal accidents that are frequent in the pressure vessel’s history. In this study, an extensive investigation of huge-flat end caps under external pressure was carried out to extract the most efficient geometrical layout. This kind of fla
In this paper, thermoelastic stress analysis of a laminated composite rotating disk has been studied using analytical and finite element methods. The governing equations of motion for a composite rotating disk are derived based on circular disk theory of plates in conjuncture with the minimum potential energy principle. The governed equations of motions are solved analytically using Differential Quadrature Method (DQM). Moreover, for the numerical simulations in FEM, ABAQUS software is used. Two models are considered in the numerical simulations for laminated solid and annular disks as, a) a disk with only one layer in longitudinal direction and layer wise in radial direction, b) a layer wise disk in both longitudinal and radial directions,
In this study, a novel approach based on multi-objective genetic algorithm (MO-GA) is used for simultaneous tuning the unscented Kalman Filter (UKF) parameters and camera and inertial measurement unit camera calibration in a vision inertial navigation system (VINS). This system consists of visual odometry and inertial navigation system (INS) which integrates with a UKF. In order to obtain simultaneous tuning and calibration of the parameters and variables, the MO-GA minimises the root mean square error of the position and velocity of the vehicle on a selected trajectory of the benchmark data set. Then, the tuned parameters and calibrated variables are placed in the VINS and an adjusted VINS (AVINS) is obtained. For investigating the AVINS,
Robustness and reliability of the designed trajectory are crucial for flight performance of launch vehicles. In this paper, robust trajectory design optimization of a typical LV is proposed. Two formulations of robust trajectory design optimization problem using single-objective and multi-objective optimization concept are presented. Both aleatory and epistemic uncertainties in model parameters and operational environment characteristics are incorporated in the problem, respectively. In order to uncertainty propagation and analysis, the improved Latin hypercube sampling is utilized. A comparison between robustness of the single-objective robust trajectory design optimization solution and deterministic design optimization solution is illustr
Optimization solutions of real-world engineering problems mainly suffer from the large computational cost, the curse of dimensionality, and the multi-disciplinary nature of the involved disciplines. These issues may be intensified by incorporating uncertainties into the design and optimization of the problem. In this context, Surrogate-Assisted Optimization (SAO) methods and Evolution Control Strategies (ECS) have been considered as powerful paradigms to overcome or at least to alleviate the mentioned issues over the last two decades. This paper presents a novel ECS strategy based on the meta-models along with the real models. This strategy calculates the accuracy of the meta-model at each design point and determines if the rea
With growing interest in low-cost, high performance and short time-to-flight satellites, the idea of using multi-purpose satellite platforms has drawn many attentions. However, under certain conditions in which the required capability of a mission is slightly more than the capabilities of a specified variant of a multi-purpose platform, it must jump to the next higher capability variant. Correspondingly, lots of unnecessary performance or capability might be imposed. In this paper, the main goal is to minimize the wasted performance in the design of an Earth Observation (EO) satellite based on a multi-purpose platform. To this end, a dynamic simulation-based model has been developed with the capability of simulating the satellite performanc
The process of plasma discharge in dielectric barrier discharge (DBD) plasma actuators can occur under two different regimes, namely uniform discharge regime and filamentary discharge regime. When the discharge becomes filamentary, the induced flow velocity and consequently, the performance of the actuator starts to decrease. Therefore, it is crucial to prevent the transition to filamentary discharge. In this paper, a model is developed to predict the formation of filamentary regime. For this purpose, the full factorial design of experiments is applied to investigate the effects of geometrical variables and electrical variables on induced flow velocity and power consumption. Then, artificial neural network (ANN) is employed to develop two m
The process of plasma discharge in dielectric barrier discharge (DBD) plasma actuators can occur under two different regimes, namely uniform discharge regime and filamentary discharge regime. When the discharge becomes filamentary, the induced flow velocity and consequently, the performance of the actuator starts to decrease. Therefore, it is crucial to prevent the transition to filamentary discharge. In this paper, a model is developed to predict the formation of filamentary regime. For this purpose, the full factorial design of experiments is applied to investigate the effects of geometrical variables and electrical variables on induced flow velocity and power consumption. Then, artificial neural network (ANN) is employed to develop two m
Dielectric barrier discharge (DBD) plasma actuators are one of the new devices for active flow control, which has received substantial attention during the last decade. The performance of the actuator is optimum when it induces the highest velocity per unit of power consumption. Since the induced velocity and the power consumption of the actuator depend on many different variables, finding the optimal set, which results in the best performance, is of immense importance. In this paper, in order to optimize the performance of these actuators, at first, by using full factorial design of experiments the effect of electrical variables (including voltage and frequency) and geometrical variables (including the gap between electrodes, dielectric th
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